#include "Perlin.h"

int permutation[] = { 151,160,137,91,90,15,
	131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
	190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
	88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
	77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
	102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
	5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
	223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
	129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
	251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
	49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
	138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
};

double fade(double t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
}

double lerp(double t, double a, double b) {
    return a + t * (b - a);
}

double grad(int hash, double x, double y, double z) {
    int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
    double u = h<8||h==12||h==13 ? x : y,   // INTO 12 GRADIENT DIRECTIONS.
		v = h<4||h==12||h==13 ? y : z;
    return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
}

double Perlin::noise(double x, double y, double z) {
    Perlin &myPerlin = Perlin::getInstance();
    int X = (int)floor(x) & 255,				// FIND UNIT CUBE THAT
        Y = (int)floor(y) & 255,				// CONTAINS POINT.
        Z = (int)floor(z) & 255;

    x -= floor(x);								// FIND RELATIVE X,Y,Z
    y -= floor(y);								// OF POINT IN CUBE.
    z -= floor(z);
    
	double u = fade(x),							// COMPUTE FADE CURVES
		v = fade(y),							// FOR EACH OF X,Y,Z.
		w = fade(z);
    
	int A = myPerlin.p[X  ]+Y, AA = myPerlin.p[A]+Z, AB = myPerlin.p[A+1]+Z,	// HASH COORDINATES OF
        B = myPerlin.p[X+1]+Y, BA = myPerlin.p[B]+Z, BB = myPerlin.p[B+1]+Z;	// THE 8 CUBE CORNERS,
	
    return lerp(w, lerp(v, lerp(u, grad(myPerlin.p[AA  ], x  , y  , z   ),		// AND ADD
								grad(myPerlin.p[BA  ], x-1, y  , z   )),		// BLENDED
						lerp(u, grad(myPerlin.p[AB  ], x  , y-1, z   ),			// RESULTS
							 grad(myPerlin.p[BB  ], x-1, y-1, z   ))),			// FROM  8
						lerp(v, lerp(u, grad(myPerlin.p[AA+1], x  , y  , z-1 ),	// CORNERS
							 grad(myPerlin.p[BA+1], x-1, y  , z-1 )),			// OF CUBE
						lerp(u, grad(myPerlin.p[AB+1], x  , y-1, z-1 ),
						  grad(myPerlin.p[BB+1], x-1, y-1, z-1 ))));
}

Perlin::Perlin () { 
    for (int i=0; i < 256 ; i++) {
        p[256+i] = p[i] = permutation[i];
    }
}
